The general plan for "status update" types of messages in Commons
3.0 is to make enhancements to the creation form and display of the
"Post" content type. You can follow any development progress on this
feature in the feature
request in the public Commons issue queue.
Several options exist for user-to-user private messaging. One
option is to use the Drupal Core user contact form to send emails from
user to user. Another is to add the Private Message module
to your Commons 3.x site.
More information about text formats